The present invention relates to an air-bag control apparatus for use in, for example, a motor vehicle and which is adapted to activate the air-bag at a satisfactory time to protect the driver and passengers during a collision.
In particular, the present invention relates to an apparatus for preventing an air-bag system from being activated by a low-velocity collision and for activating the air-bag system only at the time of a medium-velocity collision.
Conventionally, the air-bag system is activated at a time when a velocity change value obtained by integrating the deviation of the deceleration of a vehicle at the time of a collision from a predetermined threshold value has reached at least a predetermined value. The threshold value is taken as the origin. Deceleration above the threshold value is taken as a positive value (+), whereas deceleration below the threshold value is taken as a negative value (-). By thus performing a time-integral calculation, a velocity change value is derived.
Even at a low velocity (of approximately 15 km/hour), however, the velocity change value often becomes at least the predetermined value. Therefore, it is necessary to prevent activation of the air bag consequent to a low-velocity collision.
As solution thereto, JP-A-4-133840 describes a method of avoiding activation of the air bag system at a low velocity by raising the threshold value for the integral calculation of vehicle deceleration, and JP-A-3-253441 describes a method of avoiding activation of the air bag system at a low velocity by raising a predetermined value for the velocity change value after a fixed time has elapsed since the start of the calculation.
If the above described conventional techniques are used, however, the decision time of collision at the time of a collision with a medium velocity (of approximately 30 km/hour) is prolonged by raising the threshold value for the time-integration calculation of the vehicle deceleration. In addition, a change of the integral start time is increased by raising the predetermined value for the velocity change value when a fixed time has elapsed since the start of the calculation.
By appropriate design of the air bag and its electrically initiated inflator, therefore, these changes are accommodated. As a result, it takes time to manufacture the apparatus by way of empirical trials and time to make adjustments on the apparatus.
In recent years, the air bag system has been mounted not only on the driver's seat but on a passenger's seat, such as an assistant's seat. In this case, the air bag on the passenger's seat guards the passenger in cooperation with the restraint provided by a seat belt.
These two air bag systems are started at the same time and operate concurrently.